Ongoing demand for smaller electronic devices has pressured manufacturers of such devices to increase the component density and reduce the component size wherever possible within the device. To consolidate and conserve circuit board real estate, semiconductor packages may be vertically stacked to form a package-on-package (PoP) structure. A PoP structure is formed by stacking a top package on a bottom package. Electrical connections must be made between the top and bottom packages. For example, interconnections such as solder balls, copper pillars, and copper posts may be used. This typically means that the PoP structure needs additional processes or materials to form the top to bottom connection.
One way to provide this connection is through use of a substrate bar. The substrate bar is a device made separately from the top and bottom packages, and that couples the top and bottom packages in the PoP stack.
FIG. 1 is a cross-sectional view of a package substrate 100 in the prior art. The package substrate 100 of the prior art includes a carrier substrate 102 that includes a plurality of metal layers 104. A plurality of dies 106 and substrate bars 120 are mounted to carrier substrate 102. The substrate bars 120 include filled vias 122 surrounded by a substrate material 124. Filled vias 122 may be used to route electrical signals through the package substrate 100 to an external circuit. The dies 106 are electrically and mechanically connected to carrier substrate 102 through interconnections 108 (e.g., bumps). The substrate bars 120 are electrically and mechanically connected to carrier substrate 102 through interconnections 126 (e.g., bumps). A molding compound or encapsulant 110 is deposited over the dies 106 and the substrate bars 120. Lateral edges of the substrate bars 120 are not exposed. The sides of the substrate bars 120 are instead surrounded by molding compound 110.
During manufacture of the package substrate 100, the substrate bars 120 are positioned next to each of the dies 106, and then molding compound 110 is deposited over the dies 106 and bars 120. Because typical substrate bars 120 are both thin and long, the bars 120 are easily broken and hard to handle. Moreover, it is difficult to place the substrate bars 120 in an accurate position on the carrier substrate 102.
Accordingly, there is a need in the art for substrate bars that are stronger and more easily handled and assembled.